硫硅酸钙-硫铝酸钙水泥熟料矿物共存机制及性能调控

Increased attention has been given to energy saving and environmental protection, so the problem of high energy consumption and large CO2 emission of cement industry is becoming more and more serious. Therefore, the development of low-carbon cement is of great significance. Ternesite, which forms as an intermediate phase from the conversion of belite at low temperature during the production of traditional sulfoaluminate cement, is usually assumed to be inert. It has been suggested that ternesite can be activated by Al(OH)3 released during the hydration of ye’elimite and its activity is much higher than belite. In this project, a new type of low-carbon cement clinker with the coexistence of ternesite and ye’elimite is going to be studied. The calcining parameters of the formation of ternesite are determined through investigations of the effects of gypsum addition and firing temperature on the formation of ternesite. The rapid formation of ye’elimite at low temperature is promoted through ion doping and the firing schedule for the coexistence of ternesite and ye’elimite at low temperature will be proposed. Hydration kinetics of ternesite and its effect on properties of pore solution and ettringite stability are discussed. Based on the study of mechanical properties and dimensional stability of cement, the role of ternesite on cement hydration and hardening will be determined. The experiments also focus on the effect of ye’elimite on the reactivity of ternesite and establishment of the relationship between cement composition and mechanical strengths to optimize cement properties. The results of this study will make foundation for the practical application of this new type of low-carbon cement.

随着社会对节能减排和环境保护关注程度的不断增加，传统硅酸盐水泥生产能耗高、CO2排放量大的问题日益突显，因此，发展低碳水泥意义重大。硫硅酸钙是传统烧制硫铝酸盐水泥熟料由贝利特低温转化而来的惰性过渡矿物，本项目根据硫硅酸钙在硫铝酸钙水化产物铝胶作用下活性可得以有效激发并显著高于贝利特的前期研究结果，拟烧制硫硅酸钙和硫铝酸钙共存的新型低碳水泥熟料。通过分析石膏配入量和煅烧温度对硫硅酸钙形成的影响，获得硫硅酸钙烧制的工艺参数；再采取不同离子掺杂促进硫铝酸钙低温快速形成，探索有利于两种矿物低温共存的烧成工艺。探讨硫硅酸钙的水化动力学特征及其对孔溶液性质、钙矾石稳定性的影响，结合宏观力学性能和体积稳定性等研究，明确硫硅酸钙活性发挥对水泥水化硬化的作用规律。研究硫铝酸钙对硫硅酸钙活性和作用的影响，建立水泥组成匹配与力学性能之间的关系，优化水泥性能。研究成果将为此类新型低碳水泥的实际应用提供参考依据。

硫硅酸钙-硫铝酸钙水泥是一种碳排放量显著低于传统硅酸盐水泥的新型低碳水泥品种，并且硫硅酸钙活性可被硫铝酸钙水化产生的铝胶激发，有利于水泥性能的提高。但是，硫硅酸钙和硫铝酸钙的大量形成温度不一致，难以共存。本项目主要围绕以下内容开展：水泥熟料中硫硅酸钙与硫铝酸钙的共存，硫硅酸钙对水泥水化硬化的影响，养护条件对硫硅酸钙-硫铝酸钙水泥性能的影响，硫铝酸钙对硫硅酸钙水化活性的影响以及硫硅酸钙-硫铝酸钙水泥组成匹配优化。获得的主要结论如下：（1）采用离子掺杂（磷、钠）可以促进硫硅酸钙与硫铝酸钙低温共存，水泥的后期强度显著高于贝利特硫铝酸盐水泥。（2）适宜含量的硫硅酸钙能够促进水泥强度增长，并且对水泥水化产物中钙矾石的形成具有明显的促进作用。（3）养护温度升高有利于硫硅酸钙矿物早期水化，促进硫硅酸钙-硫铝酸钙水泥的强度增长，并且高温下硫硅酸钙的水化有利于钙矾石的形成和稳定。（4）硫铝酸钙能够激发硫硅酸钙的水化活性，改变养护温度和湿度会对硫硅酸钙-硫铝酸钙体系的水化造成不同程度的影响。（5）水泥中硫铝酸钙的适宜含量范围为30%~40%，硫硅酸钙的适宜含量范围为40%~55%，其优化含量根据硫铝酸钙的含量有所不同；水泥的后掺石膏优选硬石膏，其优化掺量为 8%。项目研究成果对于新型低碳水泥的开发和工程应用具有重要的科学意义。